Wyniki wyszukiwania - BazTech

1

Rapid Synthesis of Gold Nano-Particles Using Pulse Waved Potential in a Non-Aqueous Electrolyte

Jang J. G., Lee J.-O., Lee C. K.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2B

1389--1392

EN

Rapid synthesis of gold nanoparticles (AuNPs) by pulsed electrodeposition was investigated in the non-aqueous electrolyte, 1-ethyl-3-methyl-imidazoliumbis(trifluoro- methanesulfonyl)imide ([EMIM]TFSI) with gold trichloride (AuCl3). To aid the dissolution of AuCl3, 1-ethyl-3-methyl-imidazolium chloride ([EMIM]Cl) was used as a supporting electrolyte in [EMIM]TFSI. Cyclicvoltammetry experiments revealed a cathodic reaction corresponding to the reduction of gold at −0.4 V vs. Pt-QRE. To confirmthe electrodeposition process, potentiostatic electrodeposition of gold in the non-aqueous electrolyte was conducted at −0.4 V for 1 h at room temperature. To synthesize AuNPs, pulsed electrodeposition was conducted with controlled duty factor, pulse duration, and overpotential. The composition, particle-size distribution, and morphology of the AuNPs were confirmed by field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The electrodeposited AuNPs were uniformly distributed on the platinum electrode surface without any impurities arising from the non-aqueous electrolyte. The size distribution of AuNPs could be also controlled by the electrodeposition conditions.

2

A Study on Changes in Thickness of STS304 Material in the Progressive Drawing Process

Lee C. K., Kim Y. C.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2B

1319--1323

EN

In the drawing process, the roundness of corners in the punch and the die are very important factors in determining the thicknesses of the product. The results clearly revealed that the thickness of a flange was increased and the thickness of body parts reduced when the roundness of the die entrance was small. The material thickness of the top part was decreased when the corner roundness of the punch was large. The smooth inflow of materials was found to have a significant effect on the thickness during the post-process. The compressive strength of STS 304 material exhibited a higher value compared with other processing methods. Moreover, we clearly observed the corner roundness of the punch and the die to be a very important factor for STS 304 materials.

3

A Study Of The Die Roll Height Of SHP-1 And SCP-1 Materials In The Fine Blanking Process

Lee C. K., Kim Y. C.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2B

1397--1402

EN

The height of the die roll, the distance of the V-ring, and the shear rate were varied with the aim of investigating the effects of the applied changes on the fine blanking line in a cold-rolled and a pickled steel sheet, referred to as SCP-1 and SHP-1, respectively. Both materials consisted primarily of a ferrite phase with small amounts of impurities including F, Mn, and Cr. The distance was found to be a very important factor in controlling the shear of the V-ring in the fine blanking process. When the position of the V-ring was set at distances of 1.5 mm and 2 mm, the die roll height increased with increasing shear speeds from 6.4 m/min to 10 and 16 m/min. Analysis of the influence of the shear rate revealed that low rates resulted in the lowest die roll heights since the flow of material was effectively inhibited.

4

High temperature impedance spectroscopy study of non-stoichiometric bismuth zinc niobate pyrochlore

Tan K. B., Khaw C. C., Lee C. K., Zainal Z., Tan Y. P., Shaari H.

Materials Science Poland

|

2009

|

Vol. 27, No. 3

825--837

EN

Single phase non-stoichiometric bismuth zinc niobate, Bi3Zn1.84Nb3O13.84, was fabricated by a conventional solid state method. The sample was refined and fully indexed on the cubic system, space group Fd3m (No. 227), Z = 4 with A = 10.5579(4) A. Electrical characterisation was performed using an ac impedance analyser over the temperature range of 25-850 °C and frequency range of 5 Hz-13 MHz. Typical dielectric response is observed in Bi3Zn1.84Nb3O13.84 with a high relative permittivity, low dielectric loss and a negative temperature coefficient of capacitance, with the values of 147, 0.002 and -396 ppm/°C, at 100 kHz at ambient temperature, respectively. This material is highly resistive, with a conductivity of 1×10-21 A-1 Acm-1 and a high activation energy of ca. 1.59 eV.

5

High temperature impedance spectroscopy study of non-stoichiometric bismuth zinc niobate pyrochlore

Tan K. B., Khaw C. C., Lee C. K., Zainal Z., Tan Y. P., Shaari H.

Materials Science Poland

|

2009

|

Vol. 27, No. 4/1

947--959

EN

Single phase non-stoichiometric bismuth zinc niobate, Bi3Zn1.84Nb3O13.84 was prepared by a conventional solid state method. The sample was refined and fully indexed on the cubic system, space group Fd3m, Z = 4 with a = 10.5579(4) A. Electrical characterisation was performed using an ac impedance analyser over the temperature range of 25-850 °C and frequency range of 5 Hz - 3 MHz. Typical dielectric response was observed in Bi3Zn1.84Nb3O13.84with high relative permittivity, low dielectric loss and negative temperature coefficient of capacitance, with the values of 147, 0.002 and -396 ppm/°C, at 100 kHz at ambient temperature, respectively. The material is highly resistive, with the conductivity of 10-21 ohm-1ocm-1 and a high activation energy of 1.59 eV.